5.4 Results and discussion
5.4.4 Specific Combining Ability effects
5.4.4 Specific Combining Ability effects
Estimates of the specific combining ability effects of the 81 hybrids averaged across seven test locations for grain yield, NCLB reaction, plant height, ear height and plant aspect are presented in Table 5.7.
Hybrids including CML395 X CML442, DE-78-Z-126-3-2-2-1-1 X CML442, ILOO’E-1-9- 1-1-1-1-1 X CML312, X1264DW-1-2-2-2-2 X CML464 and SC22 X Gibe-1-91-1-1-1-1 had significantly positive SCA effects for grain yield. These hybrids were selected with increased grain yield level for direct production or further breeding. Three of the nine female parents [ILOO’E-1-9-1-1-1-1-1, X1264DW-1-2-2-2-2, and 124-b (113)] had significantly positive SCA effects when crossed to male parent CML202 for grain yield implying that there was positive interaction of genes between the two sets of parents.
Hybrids with high SCA effects exhibited dominance genetic effects, the basis for the expression of heterosis though epistasis genetic effect may not be ruled out. High heterosis is contributed by the complementarities of the inbred lines used in the crosses.
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Table 5.7 Estimates of specific combining ability effects of 81 maize hybrids on grain yield, NCLB reaction, plant height, ear height and plant aspect when tested at seven environments
Crosses YLD NCLB EHT PHT PASP
CML395 x CML202 -0.39538ns -1.24696* -0.1765ns -2.3542** 0.28415ns F7215 x CML202 1.45811** -0.99534ns 3.4695** 3.2648** 0.04261ns DE-78-Z x CML202 1.24557* -0.9163ns -0.9734ns 1.1442* -0.1241ns 30H83-7x CML202 1.24653* -0.0732ns -2.3369** -7.0733** 0.16609ns ILO’OE x CML202 -0.45347ns 0.08442ns 3.1393** 5.0481** -0.10161ns SZYNA x CML202 -0.0503ns 0.18394ns 4.1584** 5.1251** -0.2371ns X1264D x CML202 -0.49395ns 0.15267ns -3.9226** 0.9315ns -0.05777ns 124b(113) x CML202 0.13224ns -1.48812* -1.8257** -4.4209** 0.02952ns SC22 x CML202 1.21065* -1.13503* -1.5321** -1.6653** -0.0018ns CML395 x CML442 -0.33982ns 0.07775ns -3.6083** -4.2082** 0.10984ns F7215 x CML442 1.15795* -0.02884ns -6.1194** 0.768ns 0.01458ns DE-78-Z x CML442 -0.6603ns 0.07593ns -2.148** -0.5669ns 0.2103ns 30H83-7x CML442 -0.27649ns 0.11902ns -0.0972ns 2.4013** 0.07406ns ILO’OE x CML442 -0.01792ns -0.05907ns 0.7504ns 1.6942** -0.18835ns SZYNA x CML442 0.07383ns 0.04331ns -1.0305ns -12.7574** 0.06387ns X1264D x CML442 -0.04125ns 0.01632ns -3.2686** 1.7489** -0.18366ns 124b(113)x CML442 -0.05078ns -0.10161ns 8.4568** 4.3966** 0.02877ns SC22 x CML442 1.25478* -0.1428ns 7.0647** 6.5235** -0.1294ns CML395 x CML312 -0.613ns 0.1168ns 1.2441* -7.2138** -0.03348ns F7215 x CML312 1.44621** -0.0255ns 5.1187** 4.2339** 0.02412ns DE-78-Z x CML312 0.27367ns -0.0136ns 2.6473** 1.2418* 0.04798ns 30H83-7x CML312 0.35462ns -0.12336ns -0.5019ns -2.8185** -0.10054ns ILO’OE x CML312 -1.61109** 0.29426ns -6.6115** -10.7471** 0.27833ns SZYNA x CML312 0.31494ns -0.47479ns -0.9638ns 8.9656** -0.27559ns X1264D x CML312 -0.33871ns -0.03749ns -3.3877** 3.8005** 0.12603ns 124-b(113)x CML312 1.12605* 0.01315ns -0.5194ns 0.4339ns -0.06869ns SC22x CML312 0.34732ns 0.05053ns 2.9743** 2.1037** 0.00185ns CML395x CML464 -0.09554ns -0.10257ns 0.5139ns 0.9061ns -0.00081ns F-7215x CML464 -0.22633ns 0.02228ns -1.8543** -3.7463** 0.1825ns DE-78-Z x CML464 1.22113* -0.00511ns 0.16ns -1.8812** -0.01064ns 30H83-7x CML464 -0.46935ns 0.03085ns -2.8035** 1.1585* -0.00145ns ILO’OE x CML464 0.15208ns -0.11511ns -4.4988** -3.1772** 0.08857ns SZYNA x CML464 -0.03474ns 0.0837ns 0.1203ns 0.5426ns -0.20207ns X1264D x CML464 0.04303ns -0.11114ns 3.325** -1.5225** 0.03369ns 124-b(113)x CML464 -0.02935ns -0.0005ns 1.7076** 9.568** -0.10945ns SC22x CML464 1.13907* 0.19759ns 3.3298** -1.8479** 0.01966ns CML395 x Gibe-1-91 1.28335* -0.12463ns 0.2901ns 5.5807** -0.15958ns F-7215x Gibe-1-91 -0.20601ns -0.03836ns 7.3076** 6.6997** -0.09083ns DE-78-Z x Gibe-1-91 1.56145** -0.01931ns 0.5219ns -4.3066** 0.04274ns 30H83-7x Gibe-1-91 -0.44903ns 0.02021ns -2.1702** -3.2955** -0.17878ns ILO’OE x Gibe-1-91 1.11668* -0.00788ns -0.4511ns 1.3974* 0.14009ns SZYNA x Gibe-1-91 -0.19871ns 0.06593ns 2.025** 0.4886ns -0.12154ns X1264D x Gibe-1-91 0.06764ns -0.04677ns 2.1012** -0.5765ns 0.10136ns 124b(113) x Gibe-1-91 -0.28903ns 0.14958ns -1.2162* 0.214ns 0.03622ns SC22x Gibe-1-91 -0.58633ns 0.00124ns -8.4083** -6.2019** 0.23033ns CML395x CML445 -0.24744ns -0.01471ns -2.8718** -3.7368** -0.23604ns F-7215x CML445 1.17034* 0.11799ns -2.8543** -6.5463** -0.34929ns
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DE-78-Z x CML445 0.07208ns -0.00939ns 4.0743** 21.1759** -0.34343ns 30H83-7x CML445 -0.08268ns 0.01942ns -3.6035** -1.4701** -0.23224ns ILO’OE x CML445 -0.17697ns -0.01225ns 7.8584** -6.463** -0.27123ns SZYNA x CML445 1.24049* 0.00442ns -1.594** 1.5426** 1.81842**
X1264D x CML445 -0.19744ns -0.07257ns 1.4822** 0.1632ns -0.15753ns 124-b(113)x CML445 -0.30411ns -0.04765ns -6.4781** -5.4749** -0.1201ns SC22x CML445 1.22573* 0.01474ns 3.9869** 0.8093ns -0.10856ns CML395x CML443 1.19907* 0.00275ns 2.5012** 1.2791* 0.00192ns F-7215x CML443 -0.42173ns 0.02116ns -4.767** 1.0839ns 0.03295ns DE-78-Z x CML443 0.06287ns -0.12765ns 0.8616ns 2.5347** -0.10048ns 30H83-7x CML443 1.55526** 0.04045ns 0.5123ns 1.7315** 0.01699ns ILO’OE x CML443 0.26668ns -0.02693ns 2.4171** 6.5529** 0.0863ns SZYNA x CML443 -0.38157* -0.01741ns -0.3067ns -6.5844** -0.33548ns X1264D x CML443 0.24478* 0.22704ns -0.1162ns -5.4352** 0.01814ns 124-b(113)x CML443 0.26097ns 0.01267ns 0.6806ns -2.6304** 0.34057ns SC22x CML443 -0.41633ns -0.13209ns -1.7829** 1.468** -0.06089ns CML395x CML197 1.54605* 0.17656ns 0.5139ns 8.9569** -0.04972ns F-7215x CML197 -0.27903ns -0.08717ns 4.7028** 0.4188ns 0.11017ns DE-78-Z x CML197 -1.13014* 0.54259ns -3.24** -17.2161** 1.36803*
30H83-7x CML197 1.32367* -0.18217ns 11.525** 11.5093** 0.05907ns ILO’OE x CML197 0.25224ns -0.28526ns -5.3559** 3.0593** -0.14905ns SZYNA x CML197 -0.24459ns -0.01503ns -1.4083** 0.3077ns -0.37612ns X1264D x CML197 1.099176* 0.04013ns -0.475ns -1.8431** 0.10993ns 124-b(113)x CML197 -0.53633ns 0.02577ns -1.8496** -2.4526** -0.06978ns SC22x CML197 -0.36363ns 0.08458ns -4.4131** -2.7399** -0.00253ns CML395x A7033 0.36272ns -0.17892ns 1.5933** 0.7902ns 0.08372ns F7215x A7033 -0.89951ns 0.15378ns -5.0035** -6.1765** 0.03319ns DE-78-Z x A7033 1.15367* -0.12717ns -1.9035** -2.1257** -0.09039ns 30H83-7x A7033 -0.40252ns 0.14878ns -0.5242ns -2.1431** 0.1968ns ILO’OE x A7033 1.63176** 0.12783ns 2.752** 2.6354** 0.11696ns SZYNA x A7033 -0.21935ns -0.07407ns -1.0004ns 2.3696** -0.33439ns X1264D x A7033 0.22414ns -0.1682ns 4.2616** 2.7331** 0.0098ns 124-b(113)x A7033 1.36034* 0.05672ns 1.0441ns 0.3664ns -0.06705ns SC22x A7033 -0.27125ns 1.36124* -1.2194* 1.5505** 0.05134ns
SE 0.55 0.55 0.55 0.55 0.55
*=significant at P < 0.05, **=significant at P< 0.01
YLD=Grain yield, NCLB=Northern corn leaf blight, PHT=Plant height EHT=Ear height, PASP=Plant aspect
Hybrids such as CML395 X CML202, CML395 X CML197 and CML395 X A7033 showed significantly negative SCA effects on NCLB reaction indicating their resistance reaction against this pathogen. All other hybrids were either non-significant or had significantly positive (SC22 X A7033) SCA effect for NCLB. Hence they are not good hybrids for NCLB management. Conversely, hybrids including CML395 X CML464, CML395 X CML197, CML395 X A7033, F7215 X CML202, F7215 X CML445, SC22 X CML442, SC22 X CML312, DE-78-Z-126-3-2-2-1-1 X Gibe-1-91-1-1-1-1, 30H83-7-1-5- 1-1-1-2-1 X CML442, 30H83-7-1-5-1-1-1-2-1 X Gibe-1-91-1-1-1-1, ILOO’E-1-9-1-1-1-1-
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1 X CML464, ILOO’E-1-9-1-1-1-1-1 X A7033, SZSYNA99F2-81-4-3-1 X CML202, SZSYNA99F2-81-4-3-1 X CML442, SZSYNA99F2-81-4-3-1 X CML197, X1264DW-1-2- 2-2-2 x CML445 and 124-b (113) x CML197 had significantly negative SCA effects for plant height and ear height. These hybrids were selected for lodging tolerance. Hybrids such as CML395 x CML442, CML395 X Gibe-1-91-1-1-1-1, CML395 X CML445, F7215 X CML197, F7215 X A7033, DE-78-Z-126-3-2-2-1-1 X CML442, DE-78-Z-126-3-2-2-1-1 X CML312, DE-78-Z-126-3-2-2-1-1 X A7033, ILOO’E-1-9-1-1-1-1-1 X CML442, SZSYNA99F2-81-4-3-1 X CML312, X1264DW-1-2-2-2-2 X Gibe-1-91-1-1-1-1, 124-b (113) x CML464 and SC22 x CML443 had significant positive SCA effects for plant and ear height. As such these crosses are not desirable owing to their likely vulnerability to lodging. Hybrids such as SZSYNA99F2-81-4-3-1 X CML445 and 124-b (113) X CML464 had significantly positive SCA effects for plant aspect and are thus not recommended as good candidates for production. Sixty five of the 81 hybrids had significant SCA effects for plant height and 33 of them displayed significantly positive while 32 had significantly negative SCA effects (Table 5.7). Likewise, 30 of the 81 hybrids had significantly negative SCA effects for ear height suggesting increased lodging tolerance (Table 5.7).
The hybrids which had negative SCA effects for plant aspect were desirable and maintained for further breeding.